Space-plate arc-chute for an air-break circuit breaker

ABSTRACT

An arc-chute of the space-plate type is provide for an air-break circuit breaker in which a molded insulating casing is provided with grooves for supporting the spaced magnetizable conducting plates. The casing has an enlarged lower opening communicating with a laterally disposed restricted opening. Additionally, the insulating casing has flange, or shelf means integrally formed therewith to prevent downward movement or blasting of the arcing gases, which are heated during the arcing interrupting operation. Above the space metallic magnetizable plates are provided a plurality of spaced expansion chambers, which are partitioned from each other by vertically extending solid insulating plate portions interspersed lengthwise of the arc-chute along the upper portion thereof.

[is] 3,662,133 May 9, 1972 United States Patent Bould et al.

Frink.....................................200/146 Duvall etal............................200/147 59 66 99 .ll 00 11 o n 5 9 02 17 33 Fred Bould; John H. Taylor, both of Pittsburgh, Pa.

Primary Examiner-Robert S. Macon Attorney-A. T. Stratton, C. L. Mcl-lale and W. R. Crout ABSTRACT [73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

An arc-chute of the space-plate type is provide for an air- 22 Filed: Feb. 18,1969 [21] Appl.No.: 800,l06

.mk 27m 1 e w. m n nm Md ww .m w Ce Mm 8 .m m o. .wP m r- .mpm ma V 30 mm .n m i WW aw k. m 3V mm bP conducting plates. The casing has an enlarged lower opening posed restricted opening.

[52] U.S.Cl. 200/147 Communicating with a laterally dis [51 Additionally, the insulating casing Int. Cl. ....H0lh 33/08 h flange. or shelf means 200/147 B, 144, 147, integrally formed therewith to prevent downward movement FieldofSearch ..............i....

or blasting of the arcing gases, which are heated during the arcing interrupting operation.

UNITED STATES PATENTS Above the space metallic' magnetizable plates are provided a plurality of spaced expansion chambers, which are partitioned ee mm M p n T im m m a e m E. d m a m t mm m yw D nm 2 a 1 .mn T m vd m Wmm c m 7 tmn mm .lfl u emw mw mop fPu BJBBM 7 771 4 44/ Hflflflm 0 00 0000 2222 Latour...............................

n w a .1 rae m mm RSSP 400235 55666 99999 11111 ll/ 244 4 0 205 92592 ,2 1 89 07 623 7 ,J 22333 PATENTEBMAY 9 I972 SHEET 1 BF 7 FIG.|.

PATENTEUMM 9 I972 SHEET 2 OF 7 FA E-mam m "SHEET u m PATENTEDM 9 I972 SHEET 5 OF 7 Fred Bould 8 John H. Taylor BY A. W I ATTORNEY INVENTORS WITNESSES SPACE-PLATE ARC-CHUTE FOR AN AIR-BREAK CIRCUIT BREAKER CROSS-REFERENCES TO RELATED APPLICATIONS Certain inventions disclosed in the present application are disclosed and claimed in copending application Ser. No. 770,297, filed Oct. 24, 1968, now US. Pat. No. 3,562,459, issued Feb. 9, 1971 to Fred Bould and R. Hauser, and in copending patent application, Ser. No. 538,996, filed Mar. 31, 1966, now U.S. Pat. No. 3,427,419, issued Feb. 11, 1969 to J. D. Findley, and assigned to the assignee of the present application.

Certain additional features that are herein disclosed are disclosed and claimed in the following applications: Ser. No. 770,295, filed Oct. 24, 1968, now U.S. Pat. No. 3,569,652, issued Mar. 9, 1971 to Richard Hauser; Ser. No. 770,305, filed Oct. 24, 1968, now U.S. Pat. No. 3,544,932, issued Dec. 1, 1970 to Edmund W. Kuhn; Ser. No. 770,149, filed Oct. 24, 1968, now US. Pat. No. 3,584,170, issued June 8, 1971 to Fred Bould; and Ser. No. 770,236, filed Oct. 24, 1968, now U.S. Pat. No. 3,544,931, issued Dec. 1, 1970 to Nagar Patel.

Additional inventions disclosed in the present application are related to inventions which are disclosed and claimed in copending patent applications, Ser. No. 788,176, filed Dec. 31, 1968, now U.S. Pat. No. 3,553,534, issued Jan. 5, 1971 to Fred Bould and John H. Taylor, Ser. No. 788,168, Dec. 31, 1968, now U.S. Pat. No. 3,562,593, issued Dec. 9, 1971 to Fred Bould, and Ser. No. 779,511, filed Nov. 27, 1968, now U.S. Pat. No. 3,474,201, issued Oct. 21, 1969 to Fred Bould, which are all assigned to the same assignee as the present application.

BACKGROUND OF THE INVENTION Air-break circuit breakers have been extensively utilized by utility customers and widely used throughout the industry. A common type of air-break circuit interrupter is that of the spaced metallic plate type, in which the established arc is moved upwardly into slots provided within spaced metallic plates. Typical of such a structure is that set forth in U.S. Pat. No. 3,374,332, issued Mar. 19, 1968 to Fred Bould. Another United States patent exemplifying a typical spaced-plate type of air-break circuit interrupter is that set forth in U.S. Pat. No. 3,031,552, issued Apr. 24, 1962 to Vincent N. Stewart. Because of their wide use and extensive application, it has been endeavored by those in the manufacturing of such circuit breakers to render them of reduced cost, and highly effective in operation to enable them to span higher and higher voltage and current ratings, which are utilized on sub-transmission circuits. Typical of such ratings are 600 volts AC, 3,200 amps continuous duty and 50,000 short-circuit interrupting rating. Other ratings involve a 240 volt with interruption of 65,000 amps short-circuit rating and a continuous load-current rating of 3,200 amps. The breakers of the present invention can readily accommodate such typical ratings.

Another important problem in the design of an air-break circuit interrupter is the elimination of flame, or ionized products of composition, which are ejected upwardly through the upper open end of the arc-chute. If this flame is not deionized, it may strike adjacent grounded parts of the equipment, and may cause flashover with resultant tripping of other series circuit breakers. It is, therefore, of extreme importance to provide an improved arc-chute for such spaced-plate types of circuit interrupters, which are highly effective and additionally prevent the emission of ionized gases, or flame products externally of the arc-chute structure.

Electric circuit interrupters are used for the purpose of interrupting the flow of current in electrical power circuits. The current-interruption process is begun by separating cooperating contact members of the interrupter, whereby a gap of air or gaseous matter is opened in the circuit. The gases in the gap between the separated contact members, although normally having relatively great dielectric strength or insulating ability, may temporarily be rendered electrically conductive due to the phenomenon of ionization. If there is simultaneously a sufficient potential difference between the separated contact members, and a sufficient degree of ionization of the gases in the gap, the ionized gases will form an electric arc, which must be permanently extinguished in order to interrupt the circuit current.

When interrupting an alternating-current electrical power circuit, there are periodic current zeros, and therefore the electrical arc is discontinued naturally at the end of each half cycle. By sufficiently deionizing the gases in the gap at a current zero, reestablishment or reignition of the arc during the succeeding half-cycle can be prevented. Accordingly, it is a conventional object in designing arc-extinguishing devices for alternating-current circuit interrupters to provide suitable means for obtaining deionization of the arc gases, and otherwise impairing the conductivity of the current path, so that the potential difference between the separated contact members required to reignite the are after a current zero, known as the reignition voltage, exceeds permanently the circuit-recovery voltage impressed upon these members tending to reestablish the flow of current.

It is a well known practice in the art of electric circuit interruption to provide an arc-extinguishing device, or arc-chute having a plurality of spaced-apart metallic barriers or plates disposed across the path of the arc. These plates chop the are into a family of serially related arclets, which are subsequently deionized and extinguished as they move within the spaces between adjacent plates. Such arc-chopping metallic plates contribute to the arc-quenching process in several different ways. Their relatively cool surfaces reduce the temperature of the arc, thereby enhancing deionization and increasing are resistance. The plates cause a turbulent mixing of the hot arc gases and the relatively cool air in the spaces through which the arclets move, thereby further enhancing de-ionization. Each arclet has its own anode and cathode voltage-drop region, where the voltage gradient is relatively high. In other words, a thin cathode or anode sheath of relatively high dielectric strength is formed adjacent the opposing surfaces of each pair of metal plates, and at least a certain minimum potential difference between adjacent plates is required in order to reestablish the associated arclet after a current zero. Accordingly, the cumulative effect of a plurality of spaced metallic plates is to raise the reignition voltage of the circuit interrupter to a point where it exceeds permanently the circuitrecovery voltage.

When conventional arc-chutes of this type are properly designed and applied, the arc gases are sufficiently deionized by the action of the metallic plates to extinguish the arc. How ever, the deionization may not be sufficient to prevent reestablishment or restriking of the arc across the edges of the plates as these gases exhaust from the spaces between the plates. In order to meet this problem, it has been proposed heretofore to provide insulating members closely fitted to the upper edges of the metal plates, thereby obstructing the continuous path which would otherwise exist for the formation of an are at this point. This solution to the problem has not proved entirely satisfactory, and accordingly it is a general object of our invention to provide an improved arc-extinguisher of the spaced metallic plate type, wherein restriking of the arc after it has been extinguished by the metallic plates, is effectively prevented.

SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide an improved arc-chute for an air-break circuit interrupter of the spaced-plate type.

Another object of the present invention is the provision of an improved circuit breaker adaptable for interrupting relatively high ratings, yet eliminating the possibility of external flashover.

Still a further object of the present invention is the provision of an improved air-break type of circuit interrupter in which the strength of the several parts is increased by the provision of molded structures.

Yet a further object of the present invention is the provision of an improved arc-chute which is capable of rapid assembly and disassembly.

According to a preferred embodiment of the invention, there is provided a molded generally rectangular insulating arc-chute casing having molded on the inner walls thereof pairs of aligned grooves, in which are disposed spaced metallic magnetizable conducting plates. Above the metallic plates are provided spaced expansion chambers, which serve to assist the exhausting of the arcing gases, but the comingling of the arcing gases is prevented by spaced insulating barriers, which partition the several expansion chambers from each other.

The expansion chambers are bounded on their exhaust ends by strip portions of generally U-shaped inverted insulating plate portions, which prevent the emission of the ionized flame products, and break up the continuous path of the ionized gases by the interposition of the aforesaid spaced plate portions.

Additionally, the arcing gases are prevented from reentering the contact area by the provision of flange, or shelf portions integrally provided by the lower inner portions of the molded casing.

Finally, for certain applications, magnetizable angle-shaped plates are utilized in accommodating recesses provided at the lower extremity of the insulating casing and affixed into position by suitable sealing means.

Further objects and advantages will readily become apparent upon reading the following specification taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partly in section, of a piece of circuit-interrupting equipment utilizing a number of airbreak circuit breakers, which may be racked into position in a cell structure;

FIG. 2 is a sectional view taken along the line 1l-11 of FIG. 1 looking into the interior of the metal-clad equipment of FIG. 1 illustrating the various types of ratings, which may be accommodated by circuit-breakers of different ratings;

FIG. 3 is an enlarged vertical sectional view taken through the improved arc-chute of the present invention, the contact structure being illustrated in full lines in the closed-circuit position;

FIG. 4 is an enlarged perspective view of the arc-chute taken alone illustrating the arrangement of the various plate portions;

FIG. 5 is a horizontal plan sectional view taken along the line V-V through the arc-chute of FIG. 3 looking downwardly, the location of the separable contact structure being indicated, and being illustrated in full lines in the closedcircuit position;

FIG. 6 is a vertical sectional view taken through the insulating support for the contact structure with the arc-chute omitted for clarity;

FIG. 7 is an enlarged front elevational view of a stationary contact assembly which forms part of the circuit interrupter shown in FIG. 6.

FIG. 8 is an enlarged top plan view of the stationary contact assembly shown in FIG. 7;

FIG. 9 is an enlarged view, partly in side elevation and partly in section, of the stationary contact assembly shown in FIGS. 7 and 8 taken along the line IX--IX ofFIG. 8;

FIG. 10 is a front elevational view of a switch or contact arm, which forms part of the circuit interrupter shown in FIG.

FIG. 11 is an enlarged view, partly in side elevation and partly in section, of the movable switch or contact arm shown in FIG. 10 and its associated pivotal support; and,

FIG. 12 is an enlarged top plan view of the movable switch, or contact arm and the associated support shown in FIGS. 10 and ll.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, and more particularly to FIGS. 1 and 2, the switch gear unit 1 shown therein comprises two generally rectangular upstanding sections or cells 2 and 3 disposed in side-by-side relation. It will be understood that additional cells may be added, as desired. Generally, each cell comprises side sheets 4 and 5 and a cover sheet 6 attached to horizontal channel members 7 and 8 and vertical angle members 9 and 10 extending between and attached to the horizontal channel members 7. The channel members 8 (FIG. 1) extend between side sheets 4.

As shown more clearly in FIG. 1, each cell has a breaker compartment 11 at the front, a cable compartment 12 at the rear and a bus compartment 13 between the breaker compartment and the cable compartment.

As shown in FIG. 2, the cell 2 has four sub-compartments 11a, 11b, 11c and 11d. The sub-compartments are disposed one below the other, and they are all of the same height and width. Also, as shown in FIG. 1, circuit breaker units 14, 15 and 16 are mounted in the sub-compartments lle, 11f and 11g respectively. The compartment arrangement may be of any particular type, but a particularly desirable type from the standpoint of accommodating a number of different ratings is that set forth in patent application, Ser. No. 788,168, filed Dec. 31, 1968, now US. Pat. No. 3,562,593, issued Dec. 9, 1971 to Fred Bould and assigned to the Westinghouse Electric Corporation.

As shown in FIG. 1, each breaker unit is mounted on a track 17 in the cell and is removable horizontally from the cell. A suitable levering device 18 is provided for actuating the breaker unit to predetermined positions within the cell.

It will be observed that the breaker unit 14 may have a relatively low current-carrying capacity, the breaker unit 15 may have a higher current-carrying capacity, and the breaker unit 16 may have a still higher current-carrying capacity. As shown, the breaker units are the same width and depth but the unit 16 has a greater height than the units 14 and 15. As indicated in FIG. 2, the breaker units in the cell 2 may be of the same size as the breaker units 15. The breaker units are of the multiple type, each breaker having three poles.

As shown in FIG. 1, the breaker unit 14 has an incoming primary disconnect member 19 and an outgoing primary disconnect member 20 for each pole of the breaker unit. The disconnect members 19 and 20 are spaced vertically. Likewise, each pole of the breaker unit 15 has an incoming primary disconnect member 21 and an outgoing disconnect member 22, which are vertically spaced. The breaker unit 16 has an incoming primary disconnect member 23 and an outgoing primary disconnect member 24 for each pole of the breaker unit. The members 23 and 24 are vertically spaced.

As shown in FIG. 1, the primary disconnect members 19 engage vertical sides of horizontally extending stab conductors 2S, and the primary disconnect members 20 engage vertical sides of horizontally extending feeder conductors 26. Likewise, the primary disconnect members 21 engage stab conductors 27 and the primary disconnect members 22 engage feeder conductors 28. The primary disconnect members 23 engage stab conductors 29 and the primary disconnecting members 24 engage feeder conductors 30.

As explained hereinbefore, the breaker units 14, 15 and 16 have different current-carrying capacities. In order to obtain the additional cross-sectional area required to carry the higher currents, the vertical dimensions of the stab conductors and the feeder conductors for the breaker units are increased for the units having the higher current ratings, but the horizontal dimensions of the generally rectangular conductors remains the same. Thus, as shown in FIG. 2, the horizontal distance between pole centers for the breaker unit is of a constant value irrespective of the current ratings of the different breaker units.

As shown in FIG. 1, each primary disconnecting member comprises a plurality of pairs of vertically spaced contact fingers 31 removably mounted on a generally rectangularly conducting member 32 in the breaker unit. The contact fingers of each pair of fingers are horizontally spaced to engage vertical sides of either a stab conductor or a feeder conductor, as the case may be. Note U.S. Pat. No. 3,427,419, J. D. Findley, Jr., issued Feb. I l, 1969, in this connection. Further details of the construction are set forth in the aforesaid patent application, Ser. No. 788,168, citing the aforesaid patent.

As shown in FIG. 1, the number of contact fingers in each primary disconnecting member and the vertical dimension of the conducting members 32 of which the contact fingers are mounted, are increased as the current rating of the circuit breaker unit is increased. In this manner, the current capacity of the primary disconnecting members is increased without increasing the horizontal dimension of the disconnect member, thereby enabling the distance between the pole centers of the breaker units to be kept at a constant value irrespective of the current ratings of the breaker units.

From the foregoing description, it will be apparent that it is desirable for the individual circuit breaker units 14, 15, 16 to have a variable rating, and to be adaptable for interrupting the higher current ratings without appreciably extending the vertical height of the circuit breaker unit. To achieve this end, the arc-chute structure 34 of the present invention is particularly adapted. With reference to FIG. 3, it will be observed that, generally, there is provided a separable contact structure 36 comprising a relatively stationary contact 37 and a movable contact structure 39 situated at the end of a pivotally mounted movable contact arm 40. The pivotally mounted movable contact arm 40 is actuated by any suitable actuating mechanism, which constitutes no part of the present invention. The operating rod 41 for actuating the movable contact arm 40 is broken away, and only the inner connecting end thereof is shown in FIG. 3. The dotted lines 43 in FIG. 3 illustrate the open circuit position of the movable contact structure 39, wherein the are 33 is established and is extinguished within the arc-chute structure 34, which is disposed vertically above the area of separation of the separable contact structure 36.

FIG. 4 illustrates more in detail the internal construction of the arc-chute casing 45 and the spaced magnetic plates 46 which are disposed therein. As shown in FIGS. 3 and 4, a plurality, for example, 25 spaced slotted conducting magnetic plates 46 are disposed within the arc-chute casing 45, and are securely held in vertically extending slots or grooves 48, which are molded on the inner walls 45a, 45b of the arc-chute casing 45.

The conducting plates 46 are of a magnetizable material, such as steel, and serve to serially divide the arc 33 into a plurality of serially related arclets 33a, which extend between the magnetic plate portions 46 adjacent the apices 46a. The provision of a plurality of serially related arclets 33a increases the voltage necessary to maintain the arc and quickly brings about its extinction.

As shown in FIG. 4, it will be observed that in alignment above most of the magnetic plates 46 are a plurality of generally U-shaped inverted second insulating plates 50 having the side edges or legs 50a, 50b thereof also disposed in the same slots, or grooves 48, which accommodate the outer edges of the magnetic plates 46. The inverted U-shape insulating second plates 50 may be made of a suitable insulating material, for certain applications a glass polyester resinous material being employed.

It will be observed that the provision of the inverted U- shaped insulating plate portions 50 creates the establishment of a plurality of expansion chambers 52a, 52b, 52c etc. (FIG. 3), which are isolated and partitioned from each other by a plurality, for instance five, solid insulating first plate portions 54 which are of the same dimensions as the inverted U-shaped plates 50, but are continuous throughout their surface area.

In more detail, with reference to FIG. 3, it will be observed that there are provided five expansion chambers 52a, 52b, 52c 52d, 522, which are spaced and partitioned off from each other by the intervening solid insulating plate portions 54. Two insulating retainer strips 56 are secured by machine screws 58 (FIG. 4) at the upper extremity of the arc-chute casing 45 and serve to maintain the insulating plates 50, 54 and the magnetic plates 46 in their proper operative position.

With further reference to FIG. 4, taken in conjunction with FIG. 5, it will be observed that the arc-chute casing 45, which is preferably molded from a glass polyester resinous material, has a lower enlarged opening 60 to accommodate the point of engagement of the movable and stationary contact structure 36. In addition, the arc-chute casing 45 has a communicating relatively narrow restricted portion 61, which accommodates the opening and closing movement of the relatively more nar row movable contact 39 disposed at the upper extremity of the swinging movable contact arm 40. The dotted lines 63 in FIG. 5 more clearly show this arrangement. With further reference being directed to FIG. 4, it will be observed that the arc-chute casing 45 has a relatively wide flange, or shelf portion '65, which is adjacent the enlarged opening 60 and leads to a relatively narrow flange or shelf portion 67, which is substantially the same width as the leg portions 46b of the magnetic plates 46. This has the advantage that downward arc blow-back" is eliminated, or substantially reduced. In other words, due to the heating of the arc gases, which are, of course, ionized, it is desirable to prevent their blowing downwardly back into the area of contact separation to possibly cause a restrike. Therefore, it is desirable to keep them up within the arc-chute 34, and to achieve this end, the relatively wide flange portion 65 serves to block their downward passage.

For certain ratings, it is desirable to supplement the magnetic action of the spaced magnetic plates 46 by utilizing angle magnetizable configured metallic strips, such as the angle strips 69 shown in FIG. 4, which are disposed within recesses, which are molded are a part of the molding process for the arc-chute casing 45. When they are used, they are placed into position, and a suitable resinous material, such as a cement 70, may be used to be disposed in the area and affix them into position permanently. For certain applications, and to cheapen the construction, they may be omitted.

As shown in FIG. 4, the arc-chute structure 34 has a frontwardly extending apertured boss portion 71, which accommodates a mounting screw 72 (FIG. 3), which bolts the arc chute 34 into an operative position. An angle frame member 73, constituting a part of the circuit breaker frame unit, has a tab portion 73a extending horizontally to accommodate the shank portion of the mounting screw 72. Reference may be made to FIG. 3 in this connection A nut 74 may be used to secure the arc-chute 34 in place.

The right-hand end of the arc-chute 34, as viewed in FIG. 3, or in other words the rear portion of the arc-chute may rest upon a frame member 78, and it does not need any mounting attachment.

SEPARABLE CONTACT STRUCTURE (36) In general, the circuit breaker 14 includes an electrically insulating base member 75 (FIG. 6) which is rigidly supported on the framework of the circuit breaker 14 along with other pole units similar to the circuit breaker 14 as disclosed in greater detail in FIG. 2. The circuit breaker 14 also includes the stationary contact assembly 37 which is rigidly supported on the insulating base member 75 and which may include portions which serve as the upper terminal of the circuit breaker 14. In addition, the circuit breaker 14 includes the movable switch or contact arm 40 having movable main and arcing contact members mounted thereon, which is pivotally supported on a hinge member or pivot support member 76 (FIG. 6) which, in turn, is rigidly supported on the insulating base member 75 and which may include portions, which serve as the lower terminal of the circuit breaker 14 as viewed in FIG. 1. As shown in FIG. 6, the circuit breaker 14 may also include a pair of spaced upper and lower disconnecting contact assemblies 32, which are removably assembled on the upper and lower terminals, respectively, of the circuit breaker 14 and which are adapted to engage the upper and lower electrical conductors 25 and 26, respectively, in order to electrically connect the circuit breaker 14 to the bus bars or electrical power conductors of the associated switchgear structure (FIG. 1) which may include the cell or housing 2, 3 in which the circuit breaker 14 is normally disposed.

More specifically, the stationary contact assembly 37, as best shown in FIGS. 7 and 9, includes a plurality of support members or strap members 77, 78 and 79 which are formed from a material having a relatively high electrical conductivity, such as silver plated copper. The right-hand portions of the support or wall members 77, 78 and 79, as indicated at 77a, 78a and 79a, respectively, in FIG. 8, are disposed in tightly assembled relationship and secured or clamped together by suitable means, such as a plurality of spaced rivets 80 (FIG. 8), with the right-hand portions of said support members extending through a common opening in the upper portion 75a of the insulating base member 75 and projecting away from the rear side of the insulating base member 75, as shown in FIG. 6, to form the upper terminal of the circuit breaker 14 on which a disconnecting contact assembly 32 is assembled. The right-hand portions 78a and 79a of the outer support members 78 and 79, respectively, each includes a plurality of openings, as indicated at 79b in FIG. 9, for the support member 79 which are adapted to receive portions of the contact fingers which form part of the upper disconnecting contact assembly 32, as described in detail in the copending application, Ser. No. 538,996 now US. Pat. 3,427,419 previously mentioned, in order to retain the upper disconnecting contact assembly 32 in assembled relation with the upper terminal of the circuit breaker 14 which is formed by the portions of the support members 77, 78 and 79 just described. The left-hand portions of the outer pair of support members 77 and 79 respectively are offset in opposite directions from the associated righthand portions and spaced away from the left-hand portion of the central or intermediate support member 78 in opposite directions, as best shown in FIG. 8, with the lefthand portions of the support members 77 and 79 respectively being interconnected to the associated right-hand portions 77a and 79a respectively by the intermediate portions 77b and 79c, respectively which extend or project away from the intermediate support member 78 in opposite directions generally transversely with respect to said intermediate support member.

In order to removably secure the stationary contact assembly 37 to the upper portion 75a of the insulating base member 75, the intermediate portions 77b and 79c of the outer support members 77 and 79, respectively, include respective openings in which part of suitable fastening means, such as the nuts 81 and 82, respectively, are rigidly retained by suitable means, such as press fitting. As best shown in FIG. 6, when the stationary contact assembly 37 is assembled on the upper portion of the insulating base member 75, a pair of bolts 83 (FIG. 6) are assembled through substantially aligned openings in the upper portion and the intermediate portions of the support members 77 and 79, respectively, to engage the associated nuts 81 and 82, respectively. The bolts 83 are then tightened down until the intermediate portions bear against the upper portion of the insulating base member 75, as shown in FIG. 6.

In order to pivotally support a plurality of laterally spaced main stationary contact members 85 in the two compartments or overall cage formed between the central or intermediate support member 78 and the outer pair of support members 77 and 79 at the front side of the upper wall portion of the insulating base member 75, a pivot pin or bolt 84 is disposed to pass through substantially aligned openings in the support members 77, 78 and 79 generally transversely with respect to said support members. Suitable means, such as a lock nut 88, may be disposed on the end of the bolt 84 away from the head of the bolt 84 at one side of the stationary contact assembly 37, as best shown in FIG. 7. Each of the main stationary contact members 85 is formed from a material having a relatively high electrical conductivity such as a silver plated copper and each of said contact members includes a main stationary contact surface a which is positioned to be engaged by the movable main contact means, as will be described hereinafter, and is preferably formed from an electrically conducting material having a greater wearing ability in service, such as a silver-tungsten alloy. It is to be noted that the contact members 85 include substantially aligned openings through which the bolt 84 also passes and that said contact members are pivotally supported for movement in planes which are generally parallel to the associated support members 77, 78 and 79.

In order to provide an efficient current carrying path between the main stationary contact members 85 and the adjacent electrically conducting support members 77, 78 and 79, an electrically conducting bearing tube 114 is disposed around the intermediate portion of the bolt 84 and extends transversely between the outer support members 77 and 79 as best indicated in FIG. 7. The bearing tube 114 is preferably formed from a material having a relatively high electrical conductivity such as silver plated copper. In order to insure proper spacing of the contact member 85 along the axis of the bearing tube 114, a plurality of ring shaped spacers may be disposed between certain pairs of main stationary contact members 85, as best shown in FIG. 7.

In order to insure adequate contact pressure between the contact members 85 and the associated movable main contact means 39 mounted on the contact or switch arm 40, which will be described hereinafter, and to insure contact follow when the circuit breaker 14 opens, suitable biasing means is disposed between the intermediate support member 78 and each of the outer support members 77 and 79 as best shown in FIGS. 8 and 9. As illustrated, a compression spring 102 is disposed between a spring seat or guide 128 which bears against one of the intermediate portions of the outer support members 77 and 79, respectively, and a pair of the contact members 85. Each of the contact members 85 may include a recess which is adapted to receive the end of the associated compression spring 102 and each contact member 85 may include a projecting portion 85b which bears against one end of the associated compression spring 102 to assist in equalizing the pressure or force exerted on each contact member 85, which is biased by a particular compression spring 102. It is also important to note that the compression springs 102 also insure adequate contact pressure between each of the contact members 85 and the bearing tube 114 by biasing the upper end of each contact member 85 around the opening, through which the bearing tube 114 passes against the bearing tube 1 14.

In order to substantially prevent each of the compression springs 102 from moving out of position either laterally or in a direction transverse to the axis of a particular compression spring 102, the spring guide members 116 and 118 are disposed between each pair of compression springs 102 on opposite sides of the central support member 78 as shown in FIGS. 8 and 9. In order to retain each of the spring guide members 116 and 118 in assembled relationship and in proper position, each of said spring guide members includes a slot at the front end thereof which bears against the bearing tube 1 14, while the other end of each spring guide member projects through substantially aligned openings in one of the spring seats 128 and in the adjacent intermediate portions 77b and 790 of the outer support members 77 and 79, respectively. Since the opening in the spring seats 128 through which the associated spring guides 116 and 118 pass are close fitting, the spring guides 116 and 118 assist in properly positioning the spring seats 128 within the stationary contact assembly 37.

In order to limit the pivotal or rotational movement of the contact members 85 about the associated bolt 84, each of the contact members 85 includes a recess, as indicated at 85c in FIG. 9, which is located at the bottom end of each contact member 85. A common stop pin 83 is disposed to pass through substantially aligned openings provided in the support members 77 78 and 79 with the back edge of the recess 85: in each contact member 85 disposed to bear against the stop pin 83 under the influence of the associated biasing spring 102 when the circuit breaker 14 is in the open circuit condition, which corresponds to the position of the parts of the stationary contact assembly 37 shown in FIG. 9. In other words, the stop pin 83 limits clockwise movement of each contact member 85 under the influence of the associated compression spring 102 when the circuit breaker 14 is in the open position. When the circuit breaker 14 is in the closed position, shown in FIG. 6, the stop pin 83 is disposed intermediate the front and back edges of the recess 850 in each of the contact members 85. It is to be noted that the bearing tube 114, which is disposed on the pivot bolt 84, between the outer support members 77 and 79 also acts as a spacer member to substantially prevent overtightening of the nut 88, which is disposed at one end of the bolt 84, in order to avoid any interference with the free rotation of the contact members 85 during the operation of the circuit breaker 14. I

In order to support a pair of arcing contact members 51 and 53 on opposite sides of the intermediate support member 78 between the intermediate support member 78 and each of the adjacent outer support members 77 and 79, respectively, as best shown in FIGS. 7 and 8, a support pin or bolt 82 is disposed to pass through substantially aligned openings provided in the support members 77, 78 and 79 and in the arcing contact members 51 and 53 generally transversely with respect to the support members 77, 78 and 79, with suitable means being provided to retain the bolt 82 in assembled relation with the associated parts of the stationary contact as sembly 37, such as a lock nut 86, which is disposed at the end of the bolt 82 away from the head thereof. In order to establish adequate contact pressure between the stationary arcing contact members 51 and 53 and the movable arcing contact means 39, which is disposed on the movable contact or switch arm 40, as will be described hereinafter, the compression springs 92 and 94 are disposed on the pivot bolt 82 between the intermediate portion of the associated stationary arcing contact members 51 and 53 respectively and the adjacent outer support members 77 and 79, respectively, as best shown in FIG. 8. The compression springs 92 and 94 bias the arcing contact members 51 and 53 toward the intermediate support member 78 and toward each other, but permit lateral separating movement of the contact members 51 and 53 toward and away from each other during the operation of the circuit breaker 14 as will be described hereinafter. The arcing contact members 51 and 53 are formed from a material having a relatively high electrical conductivity, such as silver-plated copper, and include the arcing contact inserts or surfaces 62 and 64, respectively, which are located adjacent the outer ends of said arcing contact members with the arcing contact surfaces 62 and 64 facing each other, as best shown in FIG. 8, but being laterally spaced from each other a predetermined distance when the circuit breaker 14 is in the open position, which corresponds to the position of the parts shown in FIG. 8.

It is to be noted that the arcing contact members 51 and 53 include the first generally arcuate or curved portions 51a and 53a, which bear against the intermediate support member 78, which acts as a stop member to limit the movement of the arcing contact members 51 and 53 toward each other under the influence of the compression springs 92 and 94, when the circuit breaker 14 is in the open-circuit condition. The arcing contact members 51 and 53 also include the second generally arcuate or curved portions 51b and 53b adjacent the ends of said contact members away from the arcing contact surfaces 62 and 64, with the generally arcuate portions 51b and 53b acting as fulcrums or pivot surfaces when the arcing contact members 51 and 53 are actuated farther apart during the operation of the circuit breaker 14, as will be explained hereinafter. In order to guide the lateral movement of the arcing contact members 51 and 53 away and toward each other during the operation of the circuit breaker 14, the guide pin 85 is disposed to extend generally transversely between the outer support members 77 and 79, as best shown in FIG. 8,

with the guide pin passing through substantially aligned openings in the support members 77, 78 and 79 and through the slots provided at the adjacent ends of the arcing contact members 51 and 53 for the arcing contact member 51, 53 to permit the relatively separating and closing or approaching movements of the arcing contact members 51 and 53 during the operation of the circuit breaker 14. Each of the arcing contact members 51 and 53 also includes an arc runner portion, as indicated 51c, 53c for the arcing contact member 53 in FIGS. 6 and 9, which assist in carrying the arcing current which results during the operation of the circuit breaker 14 up into the associated arc extinguishing structure 34. It is to be noted that when the circuit breaker 14 is in the closed position, a current transfer path is established between the arcing contact members 51 and 53 and the intermediate electrically conducting support member 78 through the generally arcuate portions 51a and 53a and the portion of the intermediate support member 78 which is in contact with said generally arcuate portions of said arcing contact members 51, 53.

In order to pivotally support the switch or contact arm 40 at a location, which is vertically spaced from the stationary contact assembly 37 just described, the pivot support or hinge member 76 is secured to the lower portion 75b of the insulating base member 75. As best shown in FIGS. 6 and 12, the hinge member 76 includes a pair of support members 232 and 234, which are formed from a material having a relatively high electrical conductivity such as silver-plated copper. The support members 232 and 234 include the right-hand portions 232C and 234C, respectively, as viewed in FIG. 12, which extend through a common opening in the insulating base member 75 and are disposed in tightly assembled relationship with the right-hand portions 232C and 234C being secured or clamped together by suitable means, such as a plurality of spaced rivets 297, as shown in FIGS. 11 and 12, to form a lower terminal 20 of the circuit breaker 14 on which the lower disconnecting contact assembly 26 is assembled, as shown in FIG. 6. Similarly to the support members 77 and 79 previously described, each of the support members 232 and 234 include a plurality of openings as indicated at 234D in the right-hand portion 234C, which are adpated to receive portions of the contact fingers 31, which form part of the lower disconnecting contact assembly 26 and to assist in retaining the disconnecting contact assembly 26 in assembled relation with the lower terminal of the circuit breaker 14, which is formed by the support members 232 and 234, as described in greater detail in copending application, Ser. No. 538,996, now US. Pat. No. 3,427,419 previously mentioned.

In order to rigidly secure the support or hinge member 76 to the lower portion of the insulating base member 75 the intermediate portions 232B and 234B of the support members 232 and 234 respectively, which extend generally transversely with respect to the right-hand portions 232C and 234C respectively of said support members, include openings in which are secured parts of suitable fastening means, such as the nuts 276 and 278 shown in FIGS. 11 and 12, which are rigidly secured in said openings by suitable means such as press fitting. When the hinge member 76 is mounted on the insulating base member 75, a pair of bolts 279 as shown in FIG. 6 are assembled through substantially aligned openings in the lower portion 75b of the insulating base member 75 and the intermediate portions 232B and 234B of the support members 232 and 234 respectively with the ends of the bolts 279 away from the heads thereof engaging the nuts 276 and 278. The bolts 279 are then tightened down until the intermediate portions 232B and 234B of the support members 232 and 234 respectively bear against the lower portion 75b of the insulating base member 75, as shown in FIG. 6. As shown in FIG. 12, the lefthand or hinge portions of the support members 232 and 234, as indicated at 232A and 234A, respectively, are offset or laterally spaced in opposite directions from the associated right-hand portions 232C and 234C, respectively, which are interconnected to the hinge portions by the intermediate portions 232B and 234B, respectively.

In order to pivotally support the switch or contact arm 40 on the support or hinge member 76, a pivot bolt or pin 268 is provided, which passes through substantially aligned openings in the hinge portions 232A and 234A of the support member 76 and extends across the space between said hinge portions, as best shown in FIG. 12. The pivot bolt 268 may be retained in assembled relation with the hinge member 76 by suitable means such as the nut 269, which is disposed on the pivot bolt 268 at the end of said bolt away from the head thereof.

As best shown in FIG. 10, the switch or contact arm 40 includes a pair of generally U-shaped contact support members 220 and 240 which are disposed in generally nested relation with the contact support member 240 being disposed inside the contact support member 220 and with both of said contact support members 220 and 240 being pivotally supported on the pivot bolt 268. Both of the contact support members 220 and 240 are formed from a material having a relatively high electrical conductivity, such as silver-plated copper. The support member 220 includes a pair of spaced arms 220A and 220C which are interconnected by a yoke or bight portion 220B. Similarly, the support member 240 includes a pair of spaced arms 240A and 240C which are interconnected by a yoke or bight portion 240B. The arms 220A and 220C of the contact support member 220 are assembled on the pivot bolt 268 adjacent the outer sides of the hinge portions 232A and 234A respectively of the support members 232 and 234 respectively with the pivot bolt 268 passing through substantially aligned openings in said arms adjacent the ends of said arms away from the associated bight portion 220B. The arms 220A and 2208 include the raised contact portions or bosses 220D and 220E, respectively, around the openings through which the pivot bolt 268 passes, as best shown in FIG. 10. The raised contact portions 220D and 220E bear against or engage the adjacent hinge portions 232A and 234A, respectively. In order to insure adequate contact pressure between the contact portions 220D and 2205 and the hinge portions 232A and 234A, the spring washers 254 and 256 are disposed on the bolt 268 with the spring washer 254 being disposed between the head of the bolt 268 and the arm 220A of the contact support member 220 and the spring washer 256 being disposed between the nut 269 and the arm 220C of the support member 220 as best shown in FIG. 10. In order to prevent over tightening of the nut 269 which might interfere with the free rotation of the support members 220 and 240, a generally tubular spacer member 266 is disposed on the intermediate portion of the bolt 268 and extends generally transversely between the hinge portions 232A and 234A and into the substantially aligned openings of said hinge portions.

Similarly, the arms 240A and 240C includes raised contact portions or bosses 240D and 240E around the openings through which the bolt 268 passes with the raised contact portions 240D and 240E bearing against or engaging the inner sides of the hinge portions 232A and 234A respectively between which the arms 240A and 240C are disposed. In order to insure adequate contact pressure between the raised contact portions 240D and 240E on the support member 240 and the adjacent inner sides of the hinge portions 232A and 234A, respectively, the compression spring 242 is disposed on the bolt 268 around the tubular spacer member 266 as shown in FIG. and serves to bias the raised contact portions 240D and 240E against the adjacent hinge portions 232A and 234A, respectively. The arms of the contact support members 220 and 240 must be sufficiently resilient to permit deflection of the lower ends of the arms of the contact support member 220 and 240 into engagement with the hinge portions 232A and 234A under the influence of the spring washers 254 and 256 and the biasing spring 242. It is to be noted that in certain applications where the additional current carrying capacity of the contact support member 240 is not required, the contact support member 240 may be omitted along with the compression spring 242 with such a construction including only the contact support member 220 as previously described.

The movable main contact member or block 250, as best shown in FIGS. 10 and 11, is mounted or supported on the bight portions 2208 and 2408 of the support members 220 and 240 respectively and is disposed to follow a generally arcuate path about the axis of the bolt 268 when the support members 220 and 240 are actuated for rotation about the bolt 268. The movable main contact members 250 is formed from a material having a relatively high electrical conductivity, such as silver-plated copper, and includes a main contact surface or insert 252, as shown in FIGS. 11 and 12, which is formed from a material having greater wearing ability than the material from which the main contact member 250 is formed, such as silver-tungsten alloy. It is to be noted that the main contact member 250 extends substantially across the width of the switch or contact arm 40, as shown in FIG. 10, along with the main contact surface 252 which is disposed to engage the corresponding stationary main contact surface a on each of the stationary main contact members 85 which form part of the stationary contact assembly previously described in a butt type contact arrangement when the circuit breaker 14 is closed as shown in FIG. 6.

The switch or contact arm 40 also includes a pair of arcing contact members 262 and 264, as best shown in FIG. 10, which are mounted on top of the movable main contact member 250 and supported on the bight portions 2208 and 2408 of the support members 220 and 240, respectively, with the arcing contact members 262 and 264 extending or projecting radially away from the axis defined by the bolt 268. The movable arcing contact members 262 and 264 are generally L-shaped in configuration and are formed from a material having a relatively high electrical conductivity, such as copper. The movable arcing contact members 262 and 264 include the foot portions 262A and 264A, respectively, which are secured to the bight portions 2208 and 240B of the support members 220 and 240, respectively, along with the movable main contact member 250 by a pair of bolts 216 and 218 which pass through substantially aligned openings in the respective foot portions 262A and 264A, as best shown in FIG. 11, the movable main contact member 250 and the bight portions 220B and 2408 to engage the nuts 212 and 214, respectively, which are rigidly secured in corresponding openings provided in the contact support member 240 with the nuts 212 and 214 being rigidly secured in said openings by suitable means, such as press fitting. The upper portions of the arcing contact members 262 and 264 may also be rigidly secured together by suitable means, such as brazing, or by pins or rivets which pass through substantially aligned openings provided in said arcing contact members. It is important to note that the arcing contact members 262 and 264 along with the movable main contact member 250 may be readily disassembled from the switch or contact arm 40 for replacement or maintenance by loosening only a pair of the bolts 216 and 218 as just described.

A pair of arcing contact surfaces or inserts 272 and 274 are mounted on the upper portions of the movable arcing contact members 262 and 264, as best shown in FIGS. 10 and 11. The arcing contact inserts 272 and 274 are secured to the associated arcing contact members 262 and 264 by suitable means, such as brazing, and are preferably formed from a material having a relatively greater resistance to arcing such as a silver-tungsten alloy having a relatively higher proportion of tungsten. When the circuit breaker 14 is in the closed position, the arcing contact members 262 and 264 are disposed between the stationary arcing contact members 51 and 53 with the arcing contact surfaces 272 and 274 engaging or bearing against the relatively stationary arcing contact surfaces 62 and 64, respectively, which are disposed on the stationary arcing contact members 51 and 53 respectively. It is to be noted that the uppermost portions of the movable arcing contact members 262 and 264 as indicated at 262B and 264B are formed as are runners which assist in the movement of the are which normally results during an opening operation of the circuit breaker 14 into the associated arc extinguishing means 34.

In order to actuate the switch or contact arm 40 between a first position which corresponds to the closed circuit condition of the circuit breaker 14, as shown in solid lines in FIG. 6, and a second position which corresponds to the open circuit condition of the circuit breaker 14, as indicated in phantom in FIG. 6, the movable switch or contact arm 40 is operatively connected by means of the insulating operating member 41 which is pivotally connected at one end to a cross member which extends transversely through substantially aligned openings in the support members to a suitable operating mechanism which may be of the type disclosed in detail in copending application, Ser. No. 770,296, filed Oct. 24, 1968, now U.S. Pat. No., 3,590,192, issued June 29, 1971 to Bould et al.

In the operation of the circuit breaker 14 when the switch or contact arm 40 is actuated from the closed position shown in FIG. 6 by the operating mechanism which is operatively connected to the switch or contact arm 40 through the insulating operating member 41, the switch or contact arm 40 is actuated to rotate about the axis defined by the bolt 268 in a generally counterclockwise direction about said axis. It is to be noted when the circuit breaker 14 is in the closed circuit condition shown in FIG. 6, the arcing contact surfaces on the stationary arcing contact members 51 and 53 are engaged by the corresponding movable arcing contact surfaces 272 and 274, respectively, disposed on the movable arcing contact members 262 and 264, respectively, and that the movable arcing contact members 262 and 264 are disposed between the stationary arcing contact members 51 and 53 with said stationary arcing contact members being separated by a spacing greater than that shown in FIG. 8 of the drawings. The separation of the stationary arcing contact members 51 and 53 as previously explained is opposed by the forces or pressures exerted on said stationary arcing contact members by the associated compression springs 92 and 94, respectively, which insure adequate contact pressure between the arcing contact surfaces 62 and 64 and the corresponding movable arcing contact surface 272 and 274 respectively. In addition, the main stationary contact surfaces 72A on the plurality of main contact members 85 which form part of the stationary contact assembly 37 are engaged with the movable main contact surface 252 on the main movable contact member 250 in a butt type contact arrangement. It is to be noted that when the circuit breaker 14 is in the closed-circuit condition shown in FIG. 6, the plurality of contact members 85 are actuated in a counterclockwise direction about the pivot bolt 84 to further compress the biasing springs 102 and that the common stop member 83 shown in FIG. 6 is disposed intermediate the front and back edges of the recess 85c provided in each of the main stationary contact members 85, as shown in FIG. 9.

When the switch or contact arm 40 is actuated from the closed circuit position shown in FIG. 6 during an opening operation of the circuit breaker 14, the switch arm 40 will start to rotate in a counterclockwise direction about the axis defined by the bolt 268. During the initial rotational travel of the switch arm 40, the movable arcing contact surfaces 272 and 274 will remain in engagement with the associated stationary arcing contact surfaces 62 and 64 on the stationary arcing contact members 51 and 53, respectively. During the initial rotational travel of the switch arm 40, the movable main contact member or surface 252 will also remain in engagement with the main stationary contact surface 85a on each of the contact members 85 since each of the main stationary contact members 85 will follow the movement of the switch arm 40 for a relatively short distance under the influence of the compression springs 102, which will actuate the main contact members 85 in a clockwise direction about the pivot bolt 84 until the back edge of the recess 85c in each of said contact members engages the common stop member 83. When the contact members 85 engage the stop member 83 during an opening operation of the circuit breaker 14, the movable main contact surface 252 will separate from the stationary main contact surfaces 85a on each of the contact members 85 and a gap will quickly develop between the corresponding movable and stationary main contact surfaces 252 and a respectively. Meanwhile the movable arcing contact surfaces 272 and 274 will temporarily remain in engagement with the associated or corresponding stationary arcing contact surfaces 62 and 64 on the stationary arcing contact members 51 and 53 respectively to maintain a current carrying path which extends from the upper terminal formed by the support members 77, 78, 79, the arcing contact members 51 and 53, the movable arcing contact members 262 and 264, the movable main contact member 250, and the contact support members 220 and 240 of the switch arm 40 to the hinge portions 232A and 234A which then carry the current to the lower terminal formed by the support members 232 and 234. As the switch arm 40 continues to rotate in a counterclockwise direction about the axis defined by the pivot bolt 268 the movable arcing contact surfaces 272 and 274 will finally separate from the associated stationary arcing contact surfaces 62 and 64 and the are which normally results will move into the associated arc extinguishing structure 34, where the arc will be finally extinguished or interrupted during the operation of the circuit breaker. It is important to note that each of the contact support members 220 and 240 provide a pair of current carrying paths between the movable main contact member 250 and the hinge portions 232A and 234A of the support members 232 and 234, respectively, through the pairs of raised contact portions 220D and 220E and 240D and 240E, respectively. It is to be noted that a wiping action results between the movable arcing contact surfaces 272 and 274 and the associated stationary arcing contact surfaces 62 and 64 as the movable arcing contact members 262 and 264 leave the closed circuit position between the stationary arcing contact members 51 and 53 because of the biasing forces exerted on the stationary arcing contact members by the associated compression springs 92 and 94 respectively. After both the corresponding main and arcing contacts of the circuit breaker 14 separate during an opening operation of the circuit breaker 14, the switch arm 40 will continue to rotate in a counterclockwise direction about the bolt 268 until the switch arm 40 reaches the fully open position indicated in phantom in FIG. 6.

During a closing operation of the circuit breaker 14, the switch arm 40 will initially be in the open circuit position indicated in phantom in FIG. 6 and the position of the parts of the stationary contact assembly 37 which correspond to the open circuit condition of the circuit breaker 14 will be as shown in FIGS. 7 through 9. It is to be noted in FIG. 8 that the stationary arcing contact members 51 and 53 will initially be relatively closer together, as limited by the intermediate support member 78 against which the generally arcuate portions 51a and 53a bear in the open circuit condition of the circuit breaker 14, as shown in FIG. 8. In addition, each of the main,

stationary contact members 85 will engage the common stop member 83 as shown in FIG. 9 under the influence of the associated biasing springs 102 with the back edge of the recess 850 in each of the contact members 85 bearing against the common stop pin 83, as shown in FIG. 9. As the switch arm 40 is actuated from the open circuit position shown in phantom in FIG. 6 by the operating mechanism of the circuit breaker 14 through the insulating operating member 300, the switch arm 40 will rotate in a clockwise direction from the open circuit position indicated in phantom about the pivot bolt 268. During the final portion of the rotational travel of the switch arm 40 during closing operation, the movable arcing contact surfaces 272 and 274 on the movable arcing contact members 262 and 264, respectively, will first engage the corresponding stationary arcing contact surfaces 62 and 64 on the stationary arcing contact members 51 and 53 to establish a current carrying path between the upper and lower terminals of the circuit breaker 14 through the various parts previously explained during the opening operation previously described prior to the time that the movable main contact member 250 and the movable main contact surface 252 thereon engages the stationary main contact surfaces 850 on the main stationary contact members 85. As the switch arm 40 is.rotated further in a clockwise direction after the movable arcing contact surfaces 272 and 274 first engage the associated stationary arcing contact members 51 and 53 at the stationary arcing contact surfaces 62 and 64, the stationary arcing contact members 51 and 53 will be wedged or pushed farther apart than the spacing shown in FIG. 8 with the stationary arcing contact members pivoting about the generally arcuate contact portions 51a and 53a respectively until the movable arcing contact members 262 and 264 are fully engaged with the stationary arcing contact members 51 and 53 and disposed between said stationary arcing contact members as shown in FIG. 6. Any initial arcing which takes place at the separable contacts of the circuit breaker 14 will therefore take place between the movable arcing contact surfaces 272 and 274 and the corresponding stationary arcing contact surfaces 62 and 64 respectively, which are mounted on the stationary arcing contact members 51 and 53, respectively to avoid any pitting or wearing of the movable and stationary main contact members of the circuit breaker 14. As mentioned previously, the separating movement of the stationary arcing contact members 51 and 53 is guided at the ends away from the arcing contact surfaces 62 and 64 by the guide pin 85. It is to be noted that a wiping action will take place between the movable arcing contact surfaces 272 and 274 and the corresponding stationary arcing contact surfaces 62 and 64 during a closing operation of the circuit breaker 14.

When the circuit breaker 14 is called upon to carry or interrupt relatively high short circuit or fault currents, the electromagnetic forces which result due to the parallel current paths through the arms of the contact support members 220 and 240 of the switch arm 40 increase the contact pressure between the arms of each of the contact support members 220 and 240 and the associated hinge portions 232A and 234A on the opposite sides of each of which the contact arms of said support members are disposed. Similarly, when the circuit breaker 14 is called upon to close against relatively high fault currents, the parallel current paths which result through the pair of stationary arcing contact members 51 and 53 result electromagnetic forces which cause the arcing contact members 51 and 53 to be attracted toward each other and to produce a blow-on action at the arcing contact members 51 and 53 during such a closing operation. In addition, when the circuit breaker 14 is called upon to carry relatively high shortcircuit or fault currents, the current path which extends from the contact support members 220 and 240 through the main movable contact member 250 and into the main stationary contact members 85 which are each pivotally supported adjacent to the upper ends thereof includes a current loop which produces electromagnetic forces which tend to actuate each of the contact members 85 in a clockwise direction about the pivot bolt 84 and to actuate the main stationary contact surfaces 85a into engagement with the movable main contact surfaces 252 on the switch arm 40 and thus produce what may be described as a blowon" action during such an operating condition.

It is to be understood that the number of main stationary contact members or fingers 85 which are required in a particular application may vary in accordance with the current rating of the circuit breaker 14. Similarly, the current carrying capacity of the switch arm 40 may be varied in different applications by varying the number of current carrying paths between the main movable contact member 250 and the hinge portions 232A and 234A by either including or omitting the contact support member 240 where desired for a particular application. In other words, when both contact support members 220 and 240 are provided, four current carrying paths result between the main movable contact member 250 and the hinge portions 232A and 234A or if the contact support member 240 is omitted two current carrying paths will result between said hinge portions and the main movable contact member 250. In addition, the current-carrying capacity of the upper and lower terminals may be varied or reduced by modifying the shape of right-hand portions of the support members which make up the upper and lower terminals to be generally L-shaped rather than generally rectangular, as illustrated and previously described.

From the foregoing description it will be apparent that there has been provided an improved arc-chute structure 34, which is adaptable for interrupting a wide variety of ratings all within the same width and thereby enabling the circuit-breaker units l4, 15, 16 to be accommodated in the cell structures 2, 3. Additionally, the cooperation between the separable contact structure 36 and the wide and relatively narrow openings 60, 61 within the lower end of the arc chute 34 eliminates downward "blow-back of the ionized arc gases, and prevents reignition at the lower separable contact structure 36. Finally, for accommodating various ratings, the additional angle configured steel plates 69 may be utilized to intensify the magnetic field extending upwardly and through the arc-chute structure 34 to facilitate arc movement for the higher current ratings.

Although there has been illustrated and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. An arc-chute for an air-break type circuit breaker comprising, in combination, means defining a wall structure of generally rectangular shape having front and rear walls and a pair of opposed side walls defining an arcing chamber, said side walls having respective inwardly directed flange portions adjacent their lower margins extending inwardly toward each other, the inner faces of the opposed side walls being provided with a multiplicity of aligned vertical grooves, a multiplicity of horizontally spaced magnetizable conducting metallic plates disposed in said aligned vertical grooves and resting upon said inwardly directed flange portions, all of said multiplicity of metallic plates being substantially of the same height, a plurality of relatively long first imperforate insulating barrier plate members of substantially the same thickness as the metallic plate members and supported marginally at their side edges in the same vertical grooves as certain of the aforesaid metallic plates and abutting in close relationship with the tops of said certain metallic plates, a multiplicity of intervening second U-shaped insulating inverted barrier plates also supported marginally in said vertical grooves and having their outer leg portions in abutment with the other of said multiplicity of metallic plates, whereby the spaces between said leg portions of the intervening inverted second U-shaped barrier plates and the aforesaid first imperforate insulating barrier plates define a plurality of adjoining spaced expansion chambers on opposite sides of the imperforate first barrier plates to cool the exhausted arc gases prior to their upward ejection out of the arc-chute and cause less ionized material to be exhausted upwardly out of the arc-chute.

2. The arc-chute of claim 1, wherein the wall structure below the inwardly directed flange portions has a lower enlarged arc-chute opening to accommodate a relatively stationary contact means and a communicating relatively restricted opening to accommodate the opening movement of a movable contact means during the opening operation of the interrupter.

3. The arc-chute of claim 1, wherein the multiplicity of horizontally spaced magnetizable conducting metallic plates have notches provided therein to facilitate upward movement of the arc within the arc-chute.

4. The combination of claim 1, wherein the arc-chute wall structure is molded of glass polyester resinous material.

5. The combination of claim 2, wherein a pair of magnetic angle strips are located on opposite sides of the relatively restricted opening embedded within the opposed side walls of the wall structure.

6. The combination according to claim 1, wherein mounting means is provided at one end only of the arc-chute wall structure for facilitated individual arc-chute assembly and disassembly.

7. The combination according to claim 6, wherein the other end of the arc-chute wall structure has a shelf portion adapted to rest upon a frame member of a circuit-breaker unit. 

1. An arc-chute for an air-break type circuit breaker comprising, in combination, means defining a wall structure of generally rectangular shape having front and rear walls and a pair of opposed side walls defining an arcing chamber, said side walls having respective inwardly directed flange portions adjacent their lower margins extending inwardly toward each other, the inner faces of the opposed side walls being provided with a multiplicity of aligned vertical grooves, a multiplicity of horizontally spaced magnetizable conducting metallic plates disposed in said aligned vertical grooves and resting upon said inwardly directed flange portions, all of said multiplicity of metallic plates being substantially of the same height, a plurality of relatively long first imperforate insulating barrier plate members of substantially the same thickness as the metallic plate members and Supported marginally at their side edges in the same vertical grooves as certain of the aforesaid metallic plates and abutting in close relationship with the tops of said certain metallic plates, a multiplicity of intervening second U-shaped insulating inverted barrier plates also supported marginally in said vertical grooves and having their outer leg portions in abutment with the other of said multiplicity of metallic plates, whereby the spaces between said leg portions of the intervening inverted second U-shaped barrier plates and the aforesaid first imperforate insulating barrier plates define a plurality of adjoining spaced expansion chambers on opposite sides of the imperforate first barrier plates to cool the exhausted arc gases prior to their upward ejection out of the arc-chute and cause less ionized material to be exhausted upwardly out of the arcchute.
 2. The arc-chute of claim 1, wherein the wall structure below the inwardly directed flange portions has a lower enlarged arc-chute opening to accommodate a relatively stationary contact means and a communicating relatively restricted opening to accommodate the opening movement of a movable contact means during the opening operation of the interrupter.
 3. The arc-chute of claim 1, wherein the multiplicity of horizontally spaced magnetizable conducting metallic plates have notches provided therein to facilitate upward movement of the arc within the arc-chute.
 4. The combination of claim 1, wherein the arc-chute wall structure is molded of glass polyester resinous material.
 5. The combination of claim 2, wherein a pair of magnetic angle strips are located on opposite sides of the relatively restricted opening embedded within the opposed side walls of the wall structure.
 6. The combination according to claim 1, wherein mounting means is provided at one end only of the arc-chute wall structure for facilitated individual arc-chute assembly and disassembly.
 7. The combination according to claim 6, wherein the other end of the arc-chute wall structure has a shelf portion adapted to rest upon a frame member of a circuit-breaker unit. 